ErrandGirl, I am surprised they have not refered you to secondary more often. You go to LA every other weekend for 4 days since when? Since 2005? Then I am really surprised you only had 3 secondary encounters with the CBP.

You can refuse fingerprints next time, but you will risk being refused entry which would jeopardise all your future shopping trips to the USA. Unfortunately, the privacy rights have been eroding in the USA since 9/11, especially at the border and especially for foreign citizens like yourself.